: it was bill clinton with whom he would develop the closest bond. mandela, now president of south africa, visited the white house during the darkest days of the clinton presidency. he gave his friend a boost. >> our morality does not allow us to desert our friends. >> reporter: this friendship clinton treasures to this day. >> we just hit it off. i just adored him. he was always, you know, he was a true friend. >> reporter: mandela, as an ex-president, met with george w. bush in 2005. but there was no love lost there. mandela was one of bush's harshest critics when it came to iraq. when we talked to bush about the ailing mandela earlier this year, there were no hard feelings. >> he promoted freedom. he was a really great leader. he was smart and capable. and made his mark. >> reporter: obama only met mandela once. ever so briefly as a junior senator. but his connection may be the most profound. it was mandela, he says, who awakened him to the wider world. inspiring him to political activism. >> he gave me a sense of what human beings can do when guided by their hopes, not by their fears.